1-amino-2-naphthol-6-sulfonic acid is used as a photographic developer. The structure for this compound is shown below, although lone electron pairs are not shown. Which of the following bonds in the structure is the shortest?

The table below lists the specific heat capacities of several metals and liquids.

Substance

Specific Heat Capacity J/(g.oC)

Substance

Specific Heat Capacity J/(g.oC)

Al

0.902

H2O

4.18

Fe

0.451

C2H5 OH

2.46

Cu

0.383

CCl4

0.861

Au

0.128

CCl2F2

0.598

In an experiment a block of aluminum was heated to 100oC and placed in 200 g of water at 25oC. If the final temperature of the system is 43oC, and no heat transfer to the surroundings occurred, what is the mass of the aluminum block?

You are working in a forensic lab and are given a blood sample from a suspected drunk driver and asked to determine the person's blood alcohol level. The legal limit is 0.08% by mass in most states. You use the following reaction in your determination, assuming only the ethanol (C2H5OH) in the blood sample will react with the dichromate. 16H+(aq) + 2Cr2O72-(aq) + C2H5OH(l)4Cr3+(aq) + 11H2(l) + 2CO2(g)

If 14.6 mL of 0.10 M K2Cr2O7 are needed to react completely with 28 g of blood, what is the blood alcohol level of the driver?

Write an equation to describe the proton transfer that occurs when the following acid is added to water: HSO4-
Enter the products in the space below using the following as an example:
What ions are present in an aqueous calcium nitrate solution?
Ca(NO3)2(aq) Ca2+(aq) + 2NO3-(aq)
In this case, the answer would be: Ca2+(aq) + 2NO3-(aq)
You should enter: Ca^(2+) + 2NO3^(-)
In other words, use the ^ to indicate superscripts; put charges in parentheses; and leave a space on either side of the + sign. Your answer must be an exact match for the computer to grade it correctly, so be careful.

When glucose is oxidized in the human body it releases a lot of Gibbs free energy. Rather than waste this free energy, the body stores much of it in the form of ATP. The following reaction shows this process of storing some of the energy from glucose in ATP. This is an example of coupled reactions in a biological system.
The label on a can of Coke says that it contains 39 g of sugar. Assume that all of the sugar is glucose (even though it isn't), and calculate how many moles of ATP can be produced theoretically by the oxidation of 39.0 g of glucose.

To test the purity of calcium sulfate, you dissolve a 4.56g sample in water and add oxalic acid to precipitate out calcium oxalate. If 3.45g of precipitate forms, what is the percent purity of the calcium sulfate?

A standard dose of antacid as a calcium supplement is two tablets. The active ingredient in many of these tablets is calcium carbonate. One tablet, having a weight of 1.415 g, is reacted with excess HCl(aq) to produce 0.22 g CO2. What is the weight percent of calcium in this tablet?

Use the EcoRecycle Information Sheets at the Ecorecycle Victoria Plastics Recycling website to answer the following question. (Scroll down to the table called "Some uses for plastics and recycled plastics in Australia".)

Which of the following products can be made from recycled polyethylene terephthalate (PET)?

NOTE: If the link above is no longer active, click here for the information.

In one experiment chemists studied the formation of phosgene, COCl2, by mixing {y} atm of carbon monoxide and {z} atm of Cl2 in a reaction vessel at 700K. After the system reached equilibrium, the total pressure was {x} atm. Calculate Kp for the reaction.

Hint: Remember that the total pressure is the sum of all the partial pressures.

Note:
Do Not use scientific notation
DO NOT use spaces
DO NOT write in the units.
Be sure to write your answer with only one decimal place even if this is not the correct number of significant figures.

You reacted a known amount of phosphorous triiodide with excess water and determined that the percent yield of phosphoric acid was less than 100%, which of the following statements could explain why?
PI3 + 3H2O H3PO3 + 3HI

You are given a water sample to analyze from a lake contaminated with lead. It takes 24 mL of 0.020 M NaCl to exactly precipitate the Pb2+ ions from 61 mL of the water sample. What is the concentration of Pb2+ ions in the water?Pb2+(aq) + 2NaCl(aq)PbCl2(s) + 2Na+(aq)

Use the Web-Elements website to identify which of the following biologically important elements are important for nerve function.

(Once you have selected an element, you should scroll down the left frame until you see "element" around us and then select Biology. After you have selected biology once, that information will appear for all subsequent elements chosen.)

Oldhamite (CaS) has a rock salt structure like NaCl (which has interpenetrating face-centered cubic structures). The ionic radius of Ca2+ is 0.99 angstroms, and the ionic radius of S2- is 1.84 angstroms. What is the density of CaS?

The Table below lists the specific heat capacities of several metals and liquids.

Substance

Specific Heat Capacity J/(g.oC)

Substance

Specific Heat Capacity J/(g.oC)

Al

0.902

H2O

4.18

Fe

0.451

C2H5OH

2.46

Cu

0.383

CCl4

0.861

Au

0.128

CCl2F2

0.598

In an experiment, 50 g of a metal was heated to 100oC and placed in 200 g of a liquid at 25oC. Which of the following combinations of metal and liquid will produce the largest temperature increase in the liquid? (Assume that there is no transfer of energy to the surroundings.)

Students are attempting to construct a battery in the laboratory that will light up a light bulb. Compare the following lists prepared by students and determine which student will not be able to successfully build a "battery" that will light up the bulb.

Which of the following formulas represent substances that are likely to be stable at ordinary temperature and pressure? A good way to decide is to ask for which of the formulas is it possible to draw a reasonable Lewis structure (one that obeys the usual rules for drawing Lewis structures)?

From the bonds listed below, choose the one in which the highlighted atom is the partially positive end of the bond. (Try to predict electronegativity differences based on positions of the bonded atoms in the periodic table.)

H
A substance is analyzed and found to contain 57.10% carbon, 4.80% hydrogen and 38.06% oxygen by weight. Its molecular weight is determined to be 126.11 g/mol. Which of the structures shown are possible structures for the substance?

Match each of the following molecules to the best energy value for each bond. Do not use the table of bond energies in your book, but predict these values using your knowledge of bond length and bond strength.
Possible energies are: 300 kJ/mol, 330 kJ/mol, 415 kJ/mol and 950 kJ/mol.

A 25.0 mL aliquot of a 1.44M solution of ammonia (Kb = 1.8 x 10-5) is titrated with 1.50M HCl. Use the Indicator Table below to decide which of the indicators listed would most accurately signal the equivalence point for this titration.

Write the letter corresponding to your choice of indicator in the box.

You may want to use the following acid/base table to answer the question below.

Papain is a thiol protease isolated from papaya. The optimal pH for its enzymatic activity is 6.0-7.0. Which of the following buffering systems would work best for a laboratory experiment requiring active papain at pH 6.5? What molar ratios of the compounds would you use to prepare the solution?

Consider a system that has two indistinguishable molecules that can occupy three different energy levels (having energies of 1kJ, 2kJ and 3kJ, respectively). What is the probability that the molecules will have a total energy of 2 kJ?

Aluminum can be evaporated in a vacuum to form highly reflective coatings. Aluminum boils at 2792K and has a heat of vaporization of 70.0 kcal/mol. Calculate the entropy change for the vaporization of one mole of aluminum.

Steam at 100oC is condensed by an ice-water mixture at 0oC. Assuming that there is still ice present when the process is over, how much ice will be melted if 10.0 g of steam is condensed? The following may be useful:enthalpy of vaporization of water = 40.7 kJ/mol; enthalpy of fusion of water = 6.07 kJ/mol; specific heat capacity of water = 4.184 J/g•K.

One of the reactions in the process of obtaining very pure silicon for the microelectronics industry is shown below. If 24 g of SiO2 is reacted with an excess of carbon, what volume of gaseous carbon monoxide will be produced at a temperature of 17oC and a pressure of 735 mm Hg?

Consider the electrochemical cell diagram shown below. As you observe the reaction in the cell, you notice that the tin electrode seems to be disappearing while there are deposits forming on the silver electrode. Which of the following is a correct statement?

The structure and replication of DNA are strongly dependent on the hydrogen bonding system present in the double helix. How many functional groups in thymine can participate in hydrogen bonding? (This means all the groups, not just the ones that actually participate in hydrogen bonding in the double helix.)

2 SO2(g) + O2(g)
2 SO3(g)
The reaction above has an equilibrium constant of 0.25 at 830oC, and Horxn = -197.78 kJ/mol under standard conditions. Under which conditions will this reaction produce the most sulfur trioxide?

On the space shuttle, the carbon dioxide produced by the astronauts is handled by an environmental control system that utilizes the following reaction.H° = -138.4 kJ and S° = -139 J/K
Calculate G° at 25°C for this reaction.

When industrial plants burn coal, sulfur dioxide is produced. Sulfur dioxide is a primary pollutant that contributes to both industrial smog and acid rain. Is this process of producing sulfur dioxide product-favored?Using

100 g of water (c=4.184 J/g.oC), 100 g of ethanol (c=2.46 J/g.oC), 100 g of carbon tetrachloride (c=0.861 J/g.oC), and 100 g of ethylene glycol (c=2.42 J/g.oC) at 50oC were each placed into a separate coffee cup calorimeter and the temperature recorded. The temperature of the surroundings was 20oC. After one hour the temperature of which substance would have changed by the largest amount? Assume that the rate of heat transfer from the coffee cup to the surroundings was the same in each case.

Gasoline has an enthalpy of combustion of approximately 24000 kJ/gallon. When gasoline burns in an automobile engine, approximately 30% of the energy released is used to produce mechanical work. The remainder is lost as heat transfer to the engine's cooling system and eventually the atmosphere. As a start on estimating how much heat transfer is required, calculate what mass of water could be heated from 25 to 100oC by the combustion of 1.0 gallon of gasoline in an automobile.

A block of copper is heated to {x} °C and then is dropped into a coffee cup calorimeter containing {y} g of water at 25.0 °C. The final temperature of the system is 45.1 °C. What is the mass of the copper block to the nearest gram? (Assume all heat is transferred to the water). Write your answer in the box, and do NOT include units.

Stearic acid (CH3(CH2)16CO2H) is a fatty acid, the part of fat that stores most of the energy. 1.00 g of stearic acid was burned in a bomb calorimeter. The bomb had a heat capacity of 652 J/oC and a 500. g water reservoir. If the temperature rose from 25.0 to 39.3 oC, how much heat was released when the stearic acid was burned?

Sulfuric acid is added to water in a beaker and the resulting solution is much warmer than either the water or acid was initially.
Identify the following items as being part of the system or the surroundings, and indicate whether the process is exothermic or endothermic.

In a laboratory experiment to determine accurately the amount of barium in solution, aqueous sulfuric acid was added to the solution to precipitate barium sulfate, which was then filtered and weighed. In this experiment it is MOST important that ...

Lactic acid is the substance that makes your muscles burn when you've been exercising hard. Lactic acid is composed of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by weight. If it has a molar mass of 90 g/mol, what is its molecular formula?

Your TA gives you an aqueous solution containing an unknown quantity of AgNO3(aq) and an unknown quantity of Mg(NO3)2(aq). You are asked to determine the molarity of Ag+ in the solution. You add HCl(aq) to your unknown to precipitate the silver as AgCl(s), then filter out the precipitate, dry it, weigh it, and calculate the concentration of silver ion. However, your TA tells you that your calculated value of [Ag+(aq)] is lower than the actual value. Which of the following could account for your answer being too low? There may be more than one correct answer.

While working in the lab, you find a bottle of white powder labeled
"analgesic compound #5". Since the original investigator neglected
to record the identity of the substance, you decide to perform a
combustion analysis to identify the compound. You have a 65.7 g
sample that when burned produces 182 g CO2 and 51.7 g
H2O. What is the formula of this compound? (The compound
only consists of C,H, and O.)

The rainfall in central Wisconsin has a pH of 4.8 (National Atmospheric Deposition Program). Take a look at the EPA webpage Effects of Acid Rain: Lakes & Streams. This site has a chart of the pH at which several aquatic species begin to suffer. Determine which of the following species will be most affected by rainfall of this acidity if the lakes and streams in central Wisconsin aren't buffered enough to neutralize some of the acid. (There may be more than one correct answer.)

A common concentration unit used commercially is percent weight per volume (%W/V) which is the number of grams of solute in 100 mL of solution. A bottle of vinegar contains 5 %W/V acetic acid (CH3COOH). What is the molar concentration of acetic acid in the vinegar?

For the analysis of trace metals it is necessary to prepare solutions of very low concentrations from a stock solution of higher concentration using a micropipet and a volumetric flask. What volume of a 0.0010 M solution of Zn(NO3)2 (aq) would be required to prepare a 5.0 nM solution of Zn2+ in a 250mL flask?

You are given a water sample that contains ammonium chloride (NH4Cl). You determine the concentration of the salt to be 0.500 M and decide to purify the water using reverse osmosis. What is the minimum pressure that must be applied at 30.0oC to force the water through the membrane?

It takes 6.86 kg of ethylene glycol (antifreeze) to decrease the freezing point of 6.50 kg of water to -25.0oF (-31.7oC). How much sodium chloride (NaCl) would it take to decrease the freezing point of 6.50 kg of water to -25.0oF? (Assuming all the salt will dissolve in that amount of water.)

The following table illustrates the changes in emissions requirements for automobiles:

Pollutant

1970 Emissions

1990 Emissions

CA ultra-low emissions

CxHy

1.5 g/mile

0.25 g/mile

0.04 g/mile

CO

15 g/mile

3.4 g/mile

1.7 g/mile

NOx

3.1 g/mile

0.4 g/mile

0.2 g/mile

Catalytic converters are used in automobiles to convert pollutants in engine emissions to benign products. Catalytic converters in today's automobiles are made of a porous ceramic brick that has been coated with catalysts, additives, stabilizers, and support materials. Corning has developed bricks that have very thin-walled channels with 600 channels per square inch. Which of the following research goals did they target?

The activation energy for the isomerization of cyclopropane to propene is 274 kJ/mol. By what factor does the rate of reaction increase as the temperature rises from 500oC to 550oC assuming all else remains constant? (R = 8.314 J/mol k)

Hint: This is asking for the ratio of rates which is proportional to the ratio of the rate constants, all else being equal.

The isomerization of CH3NC to CH3CN has a rate constant of 0.46 s-1 at 600 K.

(1) Based on the units of the rate constant, what is the order of the reaction? {1:MULTICHOICE:zero-order#No, that is not correct.~=first-order#Correct!~second-order#No, that is not correct.~third-order#No, that is not correct.}

(2) What is the concentration of CH3CN after 0.20 minutes of reaction if the initial concentration is 0.10 M? {1:NUMERICAL:=4e-4:1e-5#Correct!~%50%4e-4:5e-5#Close, but not quite.}(Do not include units!)

Trypsin assists in digestion by breaking proteins down into smaller peptides. However, this process is not as efficient in the presence of fluorophosphates. Identify the role of each of these components.

Oxyacetylene torches used in high-temperature welding use a combination of oxygen and acetylene. The combustion of acetylene (C2H2) occurs in these torches. What volume of oxygen is needed to react with 250 mL of acetylene?

Although ozone is an important component of the upper atmosphere, long-term exposure to ozone in the air we breathe can cause inflammation of the lung, impairment of lung defense mechanisms, and irreversible changes in lung structure. The EPA has set an 8 hour limit for ozone of 0.08 ppm as an air quality standard for cities. At the EPA limit, how many ozone molecules are present in 5.0 liters of air at 25oC and 0.967 atm? (Hint: assume that air is an ideal gas and calculate the total number of molecules there are in 5.0 L. Then use the definition of ppm.)

Note: This is a calculation type question. If you exit the quiz without submitting it and you do not save an answer before exiting the quiz, the values in the question may change when you enter the quiz again.

You purchase a propane tank that can hold gas safely up to a pressure of {x} atm. When the tank contains 100. grams of propane at {y}°C, the gas exerts a pressure of {z}atm. What is the highest temperature to which the propane can be heated safely? (Report your answer in Kelvins.)

A gas phase reaction takes place in a syringe at a constant temperature and pressure. If the initial volume before reaction is 30 mL and the final volume after the reaction is complete is 15 mL, which of the following reactions took place? (Note: You can assume that you start with stoichiometric amounts of the reactants, the reaction goes to completion and that the gases behave ideally.)

Zn(OH)2 has a Ksp of 4.5 x 10-17. If you have a solution of Zn(OH)2 that has a hydroxide ion concentration equal to 4.6 x 10-6 mol/L, the solution is ... (Assume that the only relevant reaction is the solubility-product equilibrium.)

The Ksp of BaF2 is
1.7 x 10-6 mol/L in water at 25oC. What is the concentration of barium ions in equilibrium with solid barium fluoride? (Assume that the only relevant reaction is the solubility-product equilibrium.)

The molar solubility of lead(II) fluoride (PbF2) is
2.1 x 10-3 mol/L in pure water at 25oC. What is the molar solubility of lead(II) fluoride in 0.10 M NaF at 25oC? (Assume that the only relevant reaction is the solubility-product equilibrium.)

The following electrochemical data may be helpful in answering the question below.

One method for protecting metals against corrosion is to connect the metal directly to a "sacrificial anode". This is the method used to protect pipelines and ships hulls. Which of the following metals would you consider the best candidate for a sacrificial anode for a ship's hull? The hull is steel (which is mostly iron).

What makes diapers absorbent? Is peanut butter stickier than syrup or jelly? Strong, stretchy, sticky, or sweet—everything around us has special properties which make them unique. See if you can identify and compare the characteristics of materials.

Everything you see and touch has the ability to change. Sometimes substances change to form new substances. This is called a chemical change. Other times substances change but keep the same identity. This is called a physical change. Try these activities to learn more about chemical and physical change.